diff --git a/mm/swapfile.c b/mm/swapfile.c
index 312fafe..3187079 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -510,6 +510,16 @@
 }
 
 /*
+ * Called after dropping swapcache to decrease refcnt to swap entries.
+ */
+void swapcache_free(swp_entry_t entry, struct page *page)
+{
+	if (page)
+		mem_cgroup_uncharge_swapcache(page, entry);
+	return swap_free(entry);
+}
+
+/*
  * How many references to page are currently swapped out?
  */
 static inline int page_swapcount(struct page *page)
@@ -1979,6 +1989,15 @@
 	goto out;
 }
 
+/*
+ * Called when allocating swap cache for exising swap entry,
+ */
+int swapcache_prepare(swp_entry_t entry)
+{
+	return swap_duplicate(entry);
+}
+
+
 struct swap_info_struct *
 get_swap_info_struct(unsigned type)
 {